<xml>
<ToUserName><![CDATA[<{$toUsername}>]]></ToUserName>
<FromUserName><![CDATA[<{$fromUsername}>]]></FromUserName>
<CreateTime><{$time}></CreateTime>
<MsgType><![CDATA[image]]></MsgType>
<Image>
<MediaId><![CDATA[<{$media_id}>]]></MediaId>
</Image>
</xml>